Dendritic Cells and Cytokines

Abstract

Dendritic cells (DC) initiate T- and T-dependent immune responses (Austyn et al, in press; Austyn, 1992; Steinman, 1991). Different stages of the lineage are distributed within different anatomical compartments and have specialized functions that are designed to achieve this overall result. At least three specializations are apparent. First, DC progenitors that are produced within bone marrow of adult mammals travel in blood to seed the tissues. Second, within non-lymphoid tissues DC develop into an immature or “processing” stage with optimal capacities to internalize and process foreign antigens, synthesize MHC class II molecules, and assemble peptide-MHC class II complexes that can be expressed at the cell surface. Third, DC commence a maturation process within non-lymphoid tissues and migrate to secondary lymphoid tissues where, at the mature or “costimulatory” stage, the cells have optimal capacities to present foreign-peptide MHC class II complexes to resting T cells and to deliver specialized costimulatory signals for initiation of T cell activation.